A Peripheral Component Interconnect (PCI) bus is a local computer bus for attaching hardware devices in a computer. The PCI bus supports the functions found on a processor bus. Devices connected to the bus appear to the processor to be connected directly to the processor bus, and are assigned addresses in the processor's address space. Attached devices can take either the form of an integrated circuit fitted onto the motherboard itself or an expansion card that fits into a slot. PCI Express (PCIe) is a high-speed expansion to the original PCI bus standard, and offers numerous improvements including higher maximum system bus throughput, lower pin count, smaller physical footprint, and better performance-scaling for bus devices.